SAN FRANCISCO (Reuters) - The next time a terrorist aims a jet at building, maybe the plane should say no.

From computers that could steer airliners away from skyscrapers to face-recognition devices already used to spot card counters in casinos, technology could provide ways to make the skies safer, but at a cost, experts said.

Current technology, which focuses on weapons searches, was bested by terrorists armed with knives and box cutters who crashed hijacked planes into the World Trade Center and the Pentagon (news - web sites) this week. To prevent this, new security systems could be buttressed with devices that look for terrorists before boarding and ones that keep the plane safe, experts said.

Autopilots could be linked to terrain warning systems, which the Federal Aviation Administration (news - web sites) already requires in new U.S. aircraft, that show pilots what is below and recognize major landmark buildings, for instance.

"It's only a small step to take that, link it into the flight control system, and voila, you have something that you can stop things flying into buildings,'' said Ian Sheppard, of British airline consultant Air Claims